senescence means aging (not only in plants). As we know, cancer cells are immortal. but I heard that some cancer cells may produce normal cells or act like something like that and there are some researchs on this subject. but as this is a new subject i couldn't find any info. probably a PhD student ( on molecular oncology) may help me.
thanks...

2810713 wrote:If there is a genetic reason for this senescence , it may be possible for us to induce aging in cancerous cells [ cure on cancer!!] , probably scientists are looking for the same. hsg

Yes thats it. I know that gene control has an important role on senescence. unlike normal cells cancer cells netither become senescent nor goes through apoptosis. As much as I know researchers try to induce senescence and apoptosis in cancer cells.
But do all cancer cells form (by dividing) other cancer cells? Or are there any exceptions?

Normal (non-cancerous) cells can divide only a limited number of times (something like 50) before they become senescence. Tumour cells can over come this limit and can continue dividing. They are said to be "immortal". One possible mechanism (there are multiple mechanisms) for the limit on cell division in normal cells is the length of the chromosomal telomeres. Telomeres are the regions at the end of the chromosome which don't appear to code for any known genes. During each cell division the telomeres get shorter until they become very short. It has been suggested that this then exposes other genes further into the chromosome to damage / change in expression and that this causes cell senescence. Tumour cells over come this telomere shortening by producing an enzyme called "telomerase" which repairs the telomeres thus allowing continued division. Telomerase is currently a target in anticancer therapy research.

Immortalised cells are frequently used in biological research. The HeLa cells were isolated from a tumour growing in Henrietta Lacks who died in 1951. They are still growing in labs today.

If you isolate normal (non-tumour ) cells from human tissue (we used endothelial cells from the veins in human umbilical cords). they will only divide in the lab a limited number of times before they become senescent and die. Very occasionally (more come if you isolate cells from tumours) you will find some cells which keep on dividing. They have mutated and become immortalised in a similar way (probably) to how a tumour starts.